Within the field of optical media manufacture, various media formats exist. In a broad sense, optical media formats may be either preformatted or unformatted. Most conventional optical media formats include precise physical grooves in the media which are followed by the drive during reading and/or writing operation(s). The groove dimensions and spacings are precisely controlled during a mastering operation during the manufacture of the disks. In the case of read only memory formats, such as CD ROM or optical video disks, the data tracks consist of a sequence of physical groove segments, i.e. pits, which are deciphered by the disk drive as digital, audio or video information. In the case of write-once, i.e. WORM, or erasable media formats, the tracking groove is more or less continuous but has discontinuities that provide track identification information.
Conventional optical data systems typically employ a tracking servo mechanism which enables a focused spot of laser light to follow the data tracks. These tracking methods generally rely on the interaction between the optical media and the focused spot of light emitted from a laser diode. A focusing servo maintains objective-to-media distance at exactly the objective's focal length to provide diffraction limited optical spots on the media surface. Typically, the same laser beam, or beams of substantially identical wavelength, performs the tasks of servo feedback for tracking. Accordingly, the write path efficiency is reduced.